Printed circuit boards are commonly manufactured in various shapes and sizes dependent upon the environment and the apparatus for which they are intended. Such diversity of shape and size is difficult to handle and process in the commonly used automated equipment to screen print solder, to populate the printed circuit boards, and to solder the electronic components to the printed circuit board.
The automated equipment so economically advantageous and useful for high volume processing of printed circuit boards requires items to be uniformly sized and shaped for their transport through the machinery. Accordingly, to accommodate this uniform size and shape necessity, panels of printed circuit board substrates thus are sized larger than the printed circuit boards themselves and leave, for handling purposes, a "frame" of scrap or excess material surrounding the printed circuit board. Multiple circuit boards, typically identical boards, may be accommodated in varying shapes and quantities within each panel. These panels ultimately require trimming around the printed circuit board to eliminate the waste or scrap frame surrounding them.
As a final finishing step, scrap or frame material surrounding the printed circuit board has been removed from the printed circuit board by usually one of two processes. One method uses a router to rout and remove material surrounding the edges of the printed circuit board. A router is a device which may be very simple or may be highly mechanized and automated whereby a motor drives a rotary bit, the rotary bit cutting the printed circuit board substrate material at the edge of the printed circuit board, easily severing the printed circuit board from the frame of scrap material between the printed circuit board and the edge of the panels. Routers of this type may be numerically or computer controlled and typically are used in facilities manufacturing a large number of circuit boards. Routing has been the process dictated whenever the card shapes are other than "pure" rectangles, i.e., having protruding tabs for contact pads.
To rout a panel of printed circuit boards can consume several minutes. Reduce the routing time and a significantly higher number of panels can be processed by the router in the same period frame, significantly reducing the cost of the scrap separation step. The time consumed in the routing operation makes it an expensive step in printed circuit board production and a primary target for cost reduction.
A second process of excess or scrap material removal scores the panels of the printed circuit boards in such a way as to define the exterior boundaries of the printed circuit boards; this scoring weakens the scrap frame around the printed circuit boards to the point where they may be easily broken or snapped in a manual scrap removal operation. Scoring of the panel results in score lines being formed in one or preferably both faces of the printed circuit board panel. The scoring of the opposite faces of the panel is accomplished by a machine which has two opposing rotary blades which cut into the surface of the printed circuit board panel. Rotating blades close from opposite directions onto the printed circuit board; and, as the printed circuit board is translated relative to the blades, a groove is cut into each of the opposing surfaces of the printed circuit board panel, leaving a thin web of material between the two opposing grooves or score lines.
The remaining web of material extends between the printed circuit board and the scrap material surrounding it. Score lines typically extend in such a manner that they intersect at the corners of the printed circuit boards as well as extend across the frames of the scrap material. The score lines severely weaken the panel, as intended, but also affect the rigidity of the panels to the point that the panels may not be reliably handled by the automated processing equipment used on the panels, i.e., solder screening, populating of a board with electronic circuit board elements and the soldering of the elements to a circuit board.
Any panel which breaks or separates from the printed circuit board during the processing disqualifies the printed circuit board from further automated processing inasmuch as it is no longer the standardized, uniform panel required by the equipment. Frequently, the printed circuit board becomes scrap once it cannot be efficiently handled by the automated processing equipment. The separated printed circuit boards could be reworked manually; however, the cost of reworking a circuit board is prohibitive under current manufacturing techniques. Commonly, it is more economical to scrap a circuit board, even one almost completely finished, rather than to attempt to manually rework it.